Laminated structures and methods of making same



United States Patent LAlVHNATED STRUCTURES AND IVIETHODS OF MAKING SAMELucille E. Williams, Wilmington, Del., assignor to E. I. du Pont deNemours and Company, Wilmington, Del., a corporation of Delaware N0Drawing. Application March 26, 1954, Serial No. 419,103

11 Claims. (Cl. 154-128) This invention relates to laminated structures,more particularly to such structures comprising laminae of polymericlinear terephthalate esters and a copolyester, and processes of makingsuch structures.

U. S. Patent 2,465,319 describes a process for the preparation of highlypolymerized linear esters of terephthalic acid and glycols of the seriesHO(CH2)nOI-I, where n is a whole number within the range of 2 to 10.These polymeric esters may be spun into filaments and then woven intotextile fabrics. They may be cast from organic solution to prepareunsupported films. A hot plastic mass of the polymeric linearterephthalate esters may be formed into unsupported films by passing themass between smooth hot calender rolls or melt casting from a hopper.

For certain applications it is desirable to laminate a film or fabricprepared from the polyester described in U. S. Patent 2,465,319 toitself in a variety of constructions, such as, e. g. film to film,fabric to fabric and fabric to film. Also it is desirable to adhere thepolyethylene terephthalate film or fabric to chemically dissimilarsurfaces such as nylon, polyvinylidene chloride, polyacrilonitrile,glass, and various metals. Conventional adhesives do not adhere to thepolyethylene terephthalate.

Throughout the specification and appended claims the term polymericlinear terephthalate ester refers to an oriented highly polymerizedlinear ester of terephthalic acid and a glycol of the seriesHO(CH2)11.0H, where n is a whole number within the range of 2 to 10.

;It is an object of this invention to provide laminated structuresinvolving at least one lamina of a polymeric linear terephthalate esterand at least one lamina of a copolyester defined hereinafter. A furtherobject is the provision of polymeric linear terephthalate in fabric orpellicle form with a firmly adherent surface layer of a copolyester.Another object is the provision of a process for uniting a polymericlinear terephthalate ester to itself or other surfaces by means of acopolyester adhesive composition.

The broadest object of this invention is accomplished by coating a sheetof polymeric linear terephthalate with a copolyester of at least oneacryclic dicarboxylic acid and atleast one symmetrical aromaticdicarboxylic acid with a polymethylene glycolof the formula where n is aWhole number from 2 to 6 inclusive. Other objects of this invention areaccomplished by laminating a layer of a polymeric linear terephthalateester to itself or chemically dissimilar surfaces by means of acomposition comprising as an essential ingredient a copolyester such asdescribed above. a

. The polymeric linear terephthalate ester referred to in the followingspecific examples may be prepared in accordance with the teaching setforth in U. S. Patent 2,465,319 issued March 22, 1949 to J. R. Whinfieldet al. -The copolyesters employed for bonding to the polymeric linearterephthalate are similar to those prepared by "ice copolymerizing undermelt polymerization conditions, within certain composition limitshereinafter set forth, at least one acyclic dicarboxylic acid of theformula HOOO-CI-IzXCI-Iz-CO OH wherein X is a linear chain composed of 4to 9 atoms, in the chain of which not more than three may be oxygenatoms and the remaining are hydrocarbon carbon atoms, any two suchoxygen atoms being separated by at least two such carbon atoms, thehydrocarbon carbon atoms being saturated and containing a total of notmore than three hydrocarbon carbon atoms as side chain substituents,with at least one symmetrical aromatic dibasic acid from the groupconsisting of terephthalic acid, bibenzoic acid, ethylene bisp-oxybenzoic acid, tetramethylene bis p-oxybenzoic acid and2,6-naphthalic acid and with a polymethylene glycol of the formulaHO(CH2)1LOH, wherein n is a whole number from 2 to 6 inclusive.

To make the copolyesters for the purpose of this invention, it isnecessary that the aromatic acid comprise at least 30% and not more thanby weight of the total acid component of final polymer. A preferredrange is 55-65% of the aromatic acid. It is a simple matter to obtainany desired ratio of acid components in any one copolyester. The acidswill be present in the final polymer in the same ratio as they werepresent in the initial reactants, provided an excess of glycol is used.It should be understood, of course, that many combinations of thesealiphatic and aromatic acids may be used. Thus, two or more aliphaticand/or two or more aromatic acids may be used to form the copolyester.It is also to be understood that the ester-forming derivatives of theseacids can be used in place of, and are the full equivalents of, theacids described above, as is generally the case in the manufacture oflinear polyesters. The copolyesters per so are the invention of M. D.Snyder and are disclosed and claimed in U. S. Patent 2,623,033, issuedDecember 23, 1952.

The melt mixtures of polyesters and copolyesters described in U. S.Patent 2,623,031, issued December 23, 1952, to M. D. Snyder, may also beused to adhere to a surface of the polymeric linear terephthalate ester.The melt-blends are prepared by first preparing the copolyesterdescribed above and thereafter melt-blending the copolyester thus formedwith an aromatic polyester prepared by melt polymerizing a symmetricalaromatic dibasic acid from the group consisting of terephthalic acid,bibenzoic acid, tetramethylene bis p-oxybenzoic acid, and 2,6-naphthalicacid, and a polymethylene glycol of the formula HO(CH2)nOH, n being awhole number from 2 to 6 inclusive. Preferably, the same aromaticdibasic acid used in the copolyester is used in the polyester. As in thecase of the copolyester, the aromatic acid component of the melt-blendof the polyester and copolyester should be at least 30% and not morethan 70% on a weight basis.

The following specific examples are given by the way of illustration andnot limitation. The parts and percentage figures throughout thespecification and claims are expressed on a weight basis.

Example I A pellicle of polymeric linear terephthalate, 1 mil thick, wascoated on one side with a thin layer of the following adhesivecomposition:

Parts by weight Copolyester of 60 parts of ethylene terephthalate and 40parts of ethylene sebacate 16.7 Chloroform 83.3

Sufiicient composition was applied to deposit about .5

ounce persquare yard of dry coating. After the solvent wasevaporatedirom the adhesive layer, ,the dry .adhesive coating wasdoubled upon itself to form two plies of film with adhesive sandwichedbetween. The doubled film was then hot pressed at :160-.1-9,0 ,F. forabout 10 minutes at 500 poundsper square inch. After cooling to roomtemperature the adhesion :of the two plies of film was found to be 7.5pounds per one inch strip.

Example II A woven polyethylene terephtbalateffabric weighing about 3.0ounces persquare yard, haviuga thread count of 112 x 88 (warpXfiller7threads/inch) was .,coated on one side with theadhesivecompositionof .Examplel and then heated-to-evaporate the solvent..Thesdry ,adhesive film Was about ,1 .mil thick. A pellicle.o ,p,oly-vethylene terephthalate .5 m l thick was superposed .over the dryadhesive on the woven ,fabricand the ,.-assernb 1y passed betweenpressure rolls heated to about 3,00 1?. After cooling to roomtemperature the laminated .assembly was subjected to .the standardadhesion ,test by fastening one inchstrips of unlaminated,portionsof-the assemblyin the opposite jaws of aScott tester and thenmeasuring the pull required to separate the plies at a uniform rate.The,..5 mil film .oneinch .wide broke at 13.0 pounds pull without anyseparation .of the laminated portion of the assembly.

Example 111 A two mil thick film-of a copolyester of S5 part s ofethylene terephthalate and 45 parts ethylene "sebacate was sandwichedbetween a woven fabric of polyethylene terephthalate such as describedin Example .11 and a pellicle of polyethylene terephthalate ;5 milthick. The assembly was pressed between polished metal plates heated toabout 160-190" F. for 10 minutes.

The laminated assembly had the following physical properties:

Thickness p I Adhesion of laminae, 1" strip Wyzenbeek abrasionresistance (using 240 J abrading surface).

Tensile strength Tensile strength, after 48 hour immersion 132.1bs.

in sulfuric acid.

Tensile strength, after 48 hour immersion 135 lbs.

in benzene.

Tensile strength, after 48 hour immersion ,132 lbs.

in gasoline.

6 mils.

12:0 lbs. 4000 strokes.

143 lbs.

Tensile strength,afterheating-M1250 F. .ll'fi'lhs. V

for 7 days. Dielectric strengtlm 947 volts/mil.

Hydrostatic resistance, film side next 228'.260 lbs.

to water. Heat resistance, other 30 day exposure No deterioration.

at 250 F. Besistance to cracking on sharp fold:

Greased in warp direction 'No '0 r a '1; ing at minus" 100 F. Creased in.filler direction n No or ac k in g 1;

minus IQO F. Scrub 'test, dry a"- No :cracking after .500 cycles.

Scrub test, after'Z-ihour immersion in'a N0 cracking trite;

solvent mixture of: .Diisobutylene, '5 00-cycles.

b ne. o en 2 xylene, 15%.

Schiltknecht flex After 43 h $81 0? o 1 2 2 37,500 flexes. N c a kin erd r d um Benzene .vapor permeability None. Higlhntoctane gasoline vaporperme- None.

a 1 y. Benzene liquid permeability :None. High octane gasoline liquidperme- 2.

ability. v

The Wyzenheeknbrasion resistance test was carriedout in accordance withMethod 5 4 of Federal Specification GQC YT19.1I J flextilelest Methodsdated May 15,1951.

The tensile strength tests were carried out on :a .-S cott tester us nga 50 pound weight on side arm.

The dielectric strength test was carried out in accordance with theASTM'Dl lS-etd short time test in air, ,4 electrode withfiqcyclealternating current. i i 1 The hydrostatic test was carried outin accordance with Mullen AST-MD751-46T test.

The scrub test was carried out on,an.apparatus: similarito thatillustrated in Automotive Industries 49, pp. 12626.

:The Schiltkuecht flex test was carried out in accordance with test andapparatus described in Bulletin #105, pub lished by Alfred Suter, 200Fifth Avenue, New York, N. Y

The benzene vaporand'llquid permeability tests were carried out byplacing g. of benzene in a pint Mason jar. Thetest specimen ofthelaminated material was-used-asthe sealini gasket for a two piecescrew top lid with the linear polyet ylene terephthalate surface towardthe liquid. For the vapor permeability test the jars remained uprightand for the liquid permeability test the jars were turned upside down sothat the liquid contacted the test specimen. The numerical valuesreported above are the grains weight of the loss of llqu1d after 7 daysat room temperature. The test is similar to the procedure described in,ASTM 11814 161.

Example IV .A 'two mil thick film of acopolyesterof parts of ethyleneterephthalate and 40parts of ethylene ;sebacate was sandwiched between alayer of ECC1l1l2"Fiberglas andaJayerof /2 mil thick'pellicle ofpolyethylene terephthalate. The assembly was-subjected to a pressure ofabout 150 pounds per square inch at 307 F. for 10 minutes. The finalproduct had a thickness of 4 mils and was flexible. The dielectricstrength was as high as 2000voltsper millthickness. Inanattemptto-determine the bond strength of the laminate the glass fabric:tore before any stripping occurred.

Example V .A two mil thiclcfilm oiarcopolyester of 6.0-.parts:ofethylene .terephthalate and 40 parts of ethylene sebacate was superposedover'a woven polyethylene terephthalate fabric-such asdescribed .inExample ll. Theassembly was subjected to a pressure of about 50.0pounds-per square inch at 307 F. ,for 10minutes. Thetwotplies werefirmly .united together to-form acomposite assemblY- I Example VI .A .1mil: thick ,pellicle ofpolyethylene terephthalatewvas coated -on oneTSldC with the following composition:

.Parts by weight Copolyesterofiabout 65 parts of ethylenezterephtha.1ate.;and;35yparts of ethylene sebacate 22:5 Heat reactive para:tertiary .butyl phenol/formaldehyde resin Acetone Example VII A hotmelt of a 'copolyester of 30parts of ethylene terephthalate and 70'parts of ethylene 'sebacate was spread uniformly on a thin film'ofpolyethylene terephthalate. The'coated side of the'film was immediatelydoubled upon itself and the assembly was then hand pressed with asealing iron at about 194 F. Excellent adhesion was obtained between thetwo,plies ofthepolyethylene terenhthalate film.

.Ex mplaVI =A two mil thick film of a copolyester of --60-parts ofethylene terephthalate and 40 parts of 'ethylene sebacate was sandwichedbetween a one mil thick'film "ofpolyethylene terephthalate and-anylonparachute fabric weighing about'li8 ouncesper square yard. The-assemblywas subjected to a pressure of about'500 pounds :PC1"59H31' inchand atemperature ofwabout 307 -F.-'-for 10 minutes. After cooling to roomtemperature the adhesion of *the polyethylene terephthalate to thecotton fabric was found to be 4.0 pounds per one inch strip.

Example IX Example VIII was repeated with fabric woven from yarnscomposed of polyacrylonitrile in place of the nylon fabric.

The adhesion of the polyethylene terephthalate film to thepolyacrylonitrile fabric was 4.0 pounds per one inch strip.

Examples X to XV A one mil thick preformed film of a copolymercomprising 60 parts of ethylene terephthalate and 40 parts of ethylenesebacate was interposed between a three mil thick film of polyethyleneterephthalate and another lamina, as indicated in the table below. Theassemblies were preheated for 1.5 minutes at 302 F. and then subjectedto a pressure of about 3000 pounds per square inch for an additional oneminute at the same temperature. The laminates were removed from thepress and allowed to cool to room temperature. The bond strengths of thelaminates were tested and the following results were obtained:

Polyethylene Terephthalate Film 3 Bond Strength Mils Thick Adhered toVarious of Laminate Laminae by means of an Inter- Strip 1"Wide Example11 used Preformed Film 1 Mil Pounds Pull Thick of a Oopolyester of 60Parts 01' Required to Ethylene Terephthalate and 40 Separate the Partsof Ethylene Sebacate Laminae Aluminum Sheet..- 6. 6 Copper Sheet 6. 6Bronze Sheet.-- 8. 5 Tin Sheet 7. 6 Stainless Steel Sheet 5. 8 GlassSheet 1 6. 6

1 Only slight hand pressure applied after heating the assembly for 2.5minutes at 302 F.

The adhesion tests employed in all the examples were carried out inaccordance with the procedure described in Method 5950 of FederalSpecification CCC-T-l9lb, dated May 15, 1951, and entitled Textile TestMethods.

The copolyester coated pellicle or fabric of polymeric linearterephthalate ester may be adhered to the nonwoven webs described incopending applications S. N. 267,911 and S. N. 267,912, filed January23, 1952, by E. A. Rodman; S. N. 232,245, filed June 18, 1951, by J. A.Piccard, now U. S. Patent 2,676,128; and S. N. 232,247, filed June 18,1951, by E. A. Rodman.

A plurality of plies of alternating layers of the polymeric linearterephthalate and copolyester may be subjected to heat and pressure tomake rigid and semi-rigid laminates.

Due to the high strength of the polymeric linear terephthalate, films asthin as .25 mil are satisfactory for the purposes of this invention.There are no particular limits for the thickness of the polymeric linearterephthalate films in carrying out this invention. Economicconsiderations will usually control the upper limit of thickness of thepolymeric linear terephthalate films. Likewise there are no particularlimits on the weight or construction of the polymeric linearterephthalate fabrics in carrying out this invention. The polymericlinear terephthalate fabric may be woven or non-woven.

In place of the polyethylene terephthalate used in the specificexamples, it is to be understood that the highly polymerized estersobtained by the reaction of terephthalic acid and polymethylene glycolshaving more than 2 but not more than 10 methylene groups may also beused in this invention; such as, e. g. trimethylene glycol,tetramethylene glycol, pentamethylene glycol, hexamethylene glycol,heptamethylene glycol, octamethylene glycol, nonamethylene glycol, anddecamethylene glycol. The glycols having 2 to 4 methylene groups arepreferred.

The phenol-aldehyde resin employed with the copoly- 6 ester in thebonding layer of Example V1 is preferably thermosetting or heatreactive, i. e., capable of hardening or curing when heated. The resinmay be made by reacting any of the phenols with any of the aldehydes,preferably the aliphatic aldehydes. The phenol 'may be cresol, phenol,xylenol and resorcinol, as well as substituted phenols such as, e. g.para tertiary butyl phenol, para tertiary amyl phenol, para phenylphenol, or para octyl phenol. The phenolic resins may be modified withdrying oils, semi-drying oils, rosin and similar materials. Such resinsare obtainable on the open market under the proprietary names ofAmberlite, Bakelite, Beckecite, Catalin, Durez, Indur, Resinox andTexolite. The heat reactive phenol-aldehyde resin may be present in theadhesive composition in amounts up to 50% of the weight of thecopolyester.

The copolyester adhesive composition may also be used as an adherentsurface coating to the polymeric linear terephthalate esters in film orfabric form, in which case it may be desirable to add coloringmaterials, such as pigments and dyes, to the surface coating. Such acoating may be a continuous overall coating or it may be used as aprinting or stencil ink, in which case the coating is applied in theform of designs on only a portion of the surface to be coated.Furthermore, the adhesive composition may be employed as a coating foranchoring various moistureproofing coatings, e. g., polyvinylidenechloride and copolymers thereof, to polymeric linear terephthalateesters in film form.

In some cases, it may be desirable to add a plasticizer to the adhesivecomposition, and for this purpose the following materials may beemployed; sebacic or phthalic diester of monobutyl ether of ethyleneglycol, tricresyl phosphate, triphenyl phosphate, dioctyl phthalate,dibutyl phthalate and dibutyl sebacate.

The products of this invention have unusual resistance to both aromaticand aliphatic hydrocarbon liquids which make them particularly useful ascarburetor and fuel pump diaphragms, gasoline hose interiors, printersblankets, covering for electrical cables and gaskets re quiringhydrocarbon resistance.

It is apparent that many widely difierent embodiments of this inventioncan be made without departing from the spirit and scope thereof and,therefore, it is not intended to be limited except as indicated in theappended claims.

I claim:

1. A laminated assembly comprising at least three layers, the first ofwhich consists of (l) polymeric linear terephthalate ester, (2) as anintermediate layer a copolyester comprising (a) at least onepolymethylene glycol ester of an acyclic dicarboxylic acid of theformula where X is a linear chain composed of 4 to 9 atoms, in the chainof which not more than three may be oxygen atoms and the remaining arehydrocarbon carbon atoms,

any two such oxygen atoms being separated by at least two such carbonatoms, the hydrocarbon carbon atoms being saturated and containing atotal of not more than three hydrocarbon carbon atoms as side chainsubstituents; and (b) at least one polymethylene glycol ester of asymmetrical aromatic dibasic acid from the group consisting ofterephthalic acid, bibenzoic acid, ethylene bis p-oxy-benzoic acid,tetramethylene bis p-oXy-benzoic acid and 2,6-naphthalic acid, thearomatic acid comprising from 30% to 70% by weight of theacid-components of the copolyester, and the polymethylene glycolcomponent of (a) and (b) having from 2 to 6 carbon atoms, and (3) athird layer of an inorganic material selected from the group consistingof metal and glass.

2. The product of claim 1 in which the polymeric linear terephthalateester is in the form of a film.

3. The product of claim 1 in which the polymeric linear terephthalateester is in the form of a fabric.

4. The product of claim 1 in which the intermediate 7 layer (2) containsalso .a heat reactive phenolaldehyde resin.

,5'. ",Th e product of claim 4 in which the intermediate layer (Z)contains up to 50% of'the Weightof the copolyester.

6, The method of preparing laminated. assemblies which comprisesadhering the surface of a polymeric linear terephthalate ester to acopolyester, said CQPolyester comprising (a) at least one polymethyleneglycol ester of an acyclic dicarboxylic acid of the formulaHooc-.-cHi-.-X crr2-coor1 where X is a linear chain composed of 4 to 9atoms, in the chain of which not more than three may be oxygen atoms andthe remaining are hydrocarbon carbon atoms, any two such "oxygen atomsbeing separated by at least two such carbon atoms, the hydrocarboncarbon atoms being saturated and containing a total of not more thanthree hydrocarbon'carbon atoms as side chain substituents; and (b) atleast one polymethylene glycol ester of a symmetrical aromatic dibasicacid from the group consistin'g of 'terephthalic acid, bibenzoic acid,ethylene bis p-oxy-benzoic acid,jtetramethylene bis p-oxy-benzoic acidand 2,6-na'phthalic acid, the aromatic acid comprising from 30% to 70%by weight of the acid components of the 'cop'olyester, and thepolymethylene glycol component of (a) and (b)-having from 2 to 6 carbonatoms, and adhering to said copolyester layer selected from the groupconsisting of sheet metal'and glass.

7. The method of claim 6 in which the polymeric linear terephthalateester is in the form of a film.

8. The method of claim 6 in which the polymeric linear terephthalateester is in the form of a fabric.

9. The method of claim 6 in which the copolymer is applied to thepolymeric linear terephthalate ester surface in the form of a dispersionof the copolyester in an or ganic solvent.

10. The method of claim 6 in which the copolyester is applied to thepolymeric linear terephthalate ester surface in the form or" a hot melt.

11. The method which comprises adhering a polymeric linear terephthalateester surface to another surface which comprises interposing a preformedfilm of the copolyester of claim 6 between the surface of said polymericlinear terephthalate ester and said other surface, and subjecting theassembly to heat and pressure, said other surface being a memberselected from the group consisting of metal and glass.

References Cited in the tile of this patent UNITED STATES PATENTS2,465,319 Whinfield Mar. 22, 1949 2,623,031 Snyder Dec. 23, 19522,623,033 Snyder Dec. 23, 1952 2,673,826 Ness Mar. 30, 1954 2,676,128Piccard Apr. 20, 1954

6. THE METHOD OF PREPARING LAMINATED ASSEMBLIES WHICH COMPRISES ADHERINGTHE SURFACE OF A POLYMERIC LINEAR TEREPHTHALATE ESTER TO A COPOLYESTER,SAID COPOLYESTER COMPRISING (A) AT LEAST ONE POLYMETHYLENE GLYCOL ESTEROF AN ACYCLIC DICARBOXYLIC ACID OF THE FORMULA